Automatic sprinkler systems are some of the most widely used devices for fire protection. These systems have sprinklers that are activated once the ambient temperature in an environment, such as a room or building exceeds a predetermined value. Once activated, the sprinklers distribute fire-extinguishing fluid, preferably water, in the room or building. A sprinkler system is considered effective if it extinguishes or prevents growth of a fire. The effectiveness of a sprinkler is dependent upon the sprinkler consistently delivering an expected flow rate of fluid from its outlet for a given pressure at its inlet. The discharge coefficient or K-factor of a sprinkler allows for an approximation of flow rate to be expected from an outlet of a sprinkler based on the square root of the pressure of fluid fed into the inlet of the sprinkler. As used herein, the K-factor is defined as a constant representing the sprinkler discharge coefficient, that is quantified by the flow of fluid in gallons per minute (GPM) from the sprinkler outlet divided by the square root of the pressure of the flow of fluid fed into the inlet of the sprinkler passageway in pounds per square inch (PSI). The K-factor is expressed as GPM/(PSI)1/2. Industry accepted standards, such as for example, the National Fire Protection Association (NFPA) standard entitled, “NFPA 13: Standards for the Installation of Sprinkler Systems” (2010 ed.) (“NFPA 13”) and its updated edition NFPA 13 (2013 ed.), which provide for a rated or nominal K-factor or rated discharge coefficient of a sprinkler as a mean value over a K-factor range. For example for a K-factor greater than 14, NFPA 13 provides the following nominal K-factors (with the K-factor range shown in parenthesis): (i) 16.8 (16.0-17.6) GPM/(PSI)1/2; (ii) 19.6 (18.6-20.6) GPM/(PSI)1/2; (iii) 22.4 (21.3-23.5) GPM/(PSI)1/2; (iv) 25.2 (23.9-26.5) GPM/(PSI)1/2; (v) 28.0 (26.6-29.4) GPM/(PSI)1/2 or higher.
The fluid supply for a sprinkler system may include, for example, an underground water main that enters the building to supply a vertical riser. At the top of a vertical riser, an array of pipes extends throughout the fire compartment in the building. In the piping distribution network atop the riser includes branch lines that carry the pressurized supply fluid to the sprinklers. A sprinkler may extend up from a branch line, placing the sprinkler relatively close to the ceiling, or a sprinkler can be pendent below the branch line. For use with concealed piping, a flush-mounted pendent sprinkler may extend only slightly below the ceiling.
Fluid for fighting a fire can be provided to the sprinklers in various configurations. In a wet-pipe system, for buildings having heated spaces for piping branch lines, all the system pipes contain water for immediate release through any sprinkler that is activated. In a dry-pipe system, branch lines and other distribution pipes may contain a dry gas (air or nitrogen) under pressure. Dry pipe systems may be used to protect unheated open areas, cold rooms, buildings in freezing climates, cold-storage room passageways, storage or other occupancies exposed to freezing temperatures. The gas pressure in the distribution pipes may be used to hold closed a dry pipe valve at the riser to control the flow of fire fighting liquid to the distribution piping. When heat from a fire activates a sprinkler, the gas escapes and the dry-pipe valve trips, water enters branch lines, and fire fighting begins as the sprinkler distributes the fluid.
Dry sprinklers may be used where the sprinklers may be exposed to freezing temperatures. NFPA 13 defines a dry sprinkler as a “sprinkler secured to an extension nipple that has a seal at the inlet end to prevent water from entering the nipple until the sprinkler operates.” Accordingly, a dry sprinkler may include an inlet containing a seal or closure assembly, some length of tubing connected to the inlet, and a fluid deflecting structure located at the other end of the tubing. There may also be a mechanism that connects a thermally responsive component to the closure assembly. The inlet is preferably secured to a branch line by one of a threaded coupling or a clamp coupling. Depending on the particular installation, the branch line may be filled with fluid (wet pipe system) or be filled with a gas (dry pipe system). In either installation, the medium within the branch line is generally excluded from the passageway of the extension nipple or tubing of the dry sprinkler via the closure assembly in an unactuated state of the dry sprinkler. Upon activation of the thermally responsive component, the dry sprinkler is actuated and the closure assembly is displaced to permit the flow of fluid through the sprinkler.
An automatic sprinkler may be configured for addressing a fire in a particular mode such as for example, control mode or suppression mode. Fire suppression is defined by NFPA 13, Section 3.3.10 as “[s]harply reducing the heat release rate of a fire and preventing its regrowth by means of direct and sufficient application of water through the fire plume to the burning fuel surface.” A sprinkler that provides for fire suppression is a suppression mode sprinkler. A suppression mode sprinkler can be “listed” as a sprinkler that has been tested, verified and published in a list by an industry accepted organization, such as for example, FM Global (“FM”) and Underwriters Laboratories (“UL”) as a sprinkler being suitable for the specified purpose of fire suppression. UL and/or FM test and verify fire suppression performance of a sprinkler by at least installing and subjecting the sprinkler to their respective water distribution test standards: (i) UL Standard for Early-Suppression Fast-Response Sprinklers UL 1767 (2010) and (ii) FM Approval Standard Class No. 2008 (2006).
Accordingly, there are various ways of demonstrating or testing fire suppression capability of a sprinkler. For example, one way of determining the ability of a sprinkler to suppress fire in a stored commodity is by Actual Delivered Density (“ADD”) testing and comparison to Required-Delivered-Density (“RDD”) values. Briefly, ADD is defined as the amount of water flow over an area (gallons per minute over square feet or “GPM/ft2”), which is actually deposited by a particular sprinkler on top of a combustible package in order to achieve suppression and RDD is the minimum amount of water needed to suppress a particular fire. Suppression capability is believed to be quantifiable, in part, by the concepts of ADD and RDD, as developed by FM Global. Through further developments by FM Global, an ADD test can determine the ADD of a particular sprinkler configuration. The RDD value of a fire of a particular commodity tends to be fixed and therefore is presumed to be known. Under the test suppression criteria, the ADD of a particular sprinkler configuration should be higher than the RDD in order to effectively suppress a particular fire so that it does not spread beyond an initial ignition area.
Another standardized test available for demonstrating fire suppression performance is the water distribution test for Pendent ESFR Sprinklers having nominal K-factors of 14.0 and 16.8 provided under UL 1767 or FM Class Number 2008 (October 2006). Under such tests, a sprinkler can demonstrate suppression capability by delivering a water distribution density that meets or exceeds one or more of the minimum or minimum average fluid density (flow rate per area) criteria. For purposes herein, suppression performance can also be determined for sprinklers having K-factors not listed in the test standards by an appropriate equivalent requirement extrapolated from the available test standards. Suppression performance may be determined by other criteria in addition, or alternative, to the ESFR test standards, such as for example, by the hydraulic design criteria of the sprinkler and more specifically the hose stream demand criteria.
In yet another test, suppression performance of a sprinkler can be determined by actual fire testing, in which a grid of sprinklers are disposed above a storage arrangement in which a fire is ignited to actuate one or more sprinklers in the grid. Under the test criteria, suppression performance can be determined or demonstrated by the resulting number of actuated sprinklers, the maximum temperature of the storage rack over time, and/or progress of the fire in the storage arrangement, for example, containing the fire to the main array of the storage arrangement over the test duration. One or more of the above methods can be utilized to demonstrate that a sprinkler is capable of fire suppression.
Early Suppression Fast Response (ESFR) is defined under NFPA 13, Section 3.6.4.2 as a sprinkler having a thermal sensitivity, i.e., response time index (“RTI”) of 50 meter1/2second1/2 (“m1/2sec1/2”) or less and “listed” for its capability to provide fire suppression of specific high-challenge fire challenges. The “RTI” is a measure of thermal sensitivity and is related to the thermal inertia of a heat responsive element of a sprinkler. While ESFR sprinklers can be defined by the RTI of the sprinkler and its performance under the test standards, it should be understood that “suppression” mode sprinklers are not necessarily limited to ESFR sprinklers or sprinklers having an RTI of 50 or less. Accordingly, suppression mode sprinklers satisfying standardized test and/or other suppression criteria may have a thermally sensitive trigger having an RTI of ordinary or standard response sprinklers, i.e., RTI of 80 or greater.
U.S. Patent Publication No. 2009/0294138 shows and describes a dry sprinkler and in particular a dry ESFR sprinkler having a K-factor of 14 or greater. A known ESFR dry sprinkler is shown and described in Viking Technical Data Sheet, entitled “ESFR Dry Pendent Sprinkler VK501 (K14.0)” (Sep. 13, 2012).